Join in expert discussion on the topics of Astronomy, astrophysics and cosmology. This may include discussion on celestial objects, space, and the physical universe as a whole. Mainstream science only.
Threads
Undergrad Why does a 2000 K metal glow white while Arcturus at 4300 K appears orange?
- bruha
- · Replies 10 ·
Graduate Dark matter and spacetime metric
- Angelika10
- · Replies 8 ·
High School Naked Singularity, Black hole mass limit
- Arman777
- · Replies 12 ·
Undergrad Supermassive singularity the cause of the Big Bang?
- Marcus Gross
- · Replies 32 ·
Undergrad The Universe as an isolated system
- Trust10
- · Replies 27 ·
High School The unusual motion of stars in galaxies
- Wallsy
- · Replies 6 ·
Undergrad Dark energy and the rotation curve of spiral galaxies
- Apashanka
- · Replies 1 ·
High School Active galaxies point to new physics of cosmic expansion
- wolram
- · Replies 2 ·
Undergrad Does all orbiting space debris eventually fall and why?
- Jonathan212
- · Replies 5 ·
Undergrad Inflation and the size of the Universe
- Ranku
- · Replies 9 ·
Stargazing Lunar eclipse on January 21, 2019 with possible meteoroid impact
- russ_watters
- · Replies 31 ·
Undergrad Solar radiation at same latitude in different continents and future eccentricity effects
- QuarkDecay
- · Replies 5 ·
Undergrad Why Are Star Spectra Shown as Absorption Rather Than Emission?
- nmsurobert
- · Replies 3 ·
Graduate ALMA's first VLBI observations of Sagittarius A* at 86 GHz
- Auto-Didact
- · Replies 3 ·
Graduate Schrödinger Evolution of Self-Gravitating Disks
- Auto-Didact
- · Replies 1 ·
Undergrad Why hasn't the Oort cloud flattened into a disk?
- Jonathan212
- · Replies 33 ·
Undergrad What is the Hubble Parameter over time and how can I calculate it?
- Arman777
- · Replies 2 ·
Undergrad Relating comoving distance to luminosity distance in expanding universe
- Apashanka
- · Replies 15 ·
Stargazing Seeing star light -- Why does it take so long?
- Don H
- · Replies 19 ·
High School Algebraic Topology in the tv show The Big Bang Theory
- tylerfarzam
- · Replies 11 ·
High School Galaxy rotational curves vs time
- Daniel Dimov
- · Replies 9 ·
Undergrad Relationship between Energy density and Curvature
- Arman777
- · Replies 27 ·
Undergrad Opal Crystals on Mars: Implications for Geochemical Conditions
- Edge5
- · Replies 3 ·
Undergrad Sachs-Wolfe effect and Superclusters/Supervoids
- Arman777
- · Replies 7 ·
High School How Old is the Milky Way Galaxy?
- Simon Peach
- · Replies 12 ·
Graduate How do I define Open cluster membership?
- tomwilliam
- · Replies 5 ·
Undergrad Relativistic Reference Frames and the Big Bang?
- jahzam
- · Replies 6 ·
High School Is Dark Energy really the best term?
- StarTrekkin
- · Replies 7 ·
Undergrad What Are the Boundaries of a Flat and Saddle-Shaped Universe?
- msailer1234
- · Replies 24 ·
Graduate How Does Stellar Radiation Clear Dust from a Proto-Planetary Disc?
- RJ Emery
- · Replies 4 ·
High School Are there physical objects between galaxies?
- kechloo
- · Replies 5 ·
Undergrad What are the latest thoughts about the timescape cosmology
- Arman777
- · Replies 12 ·
High School Exoplanets - Suspicious evidence and fantastical conclusions
- PaulCam
- · Replies 21 ·
Stargazing Optimizing DSS stacking and post-processing for urban astrophotography
- Andy Resnick
- · Replies 43 ·
Undergrad Theory behind how expansion moves mass but doesn't interfere with inertia?
- Rodney-Believes
- · Replies 21 ·
Graduate Lagrangian vs pseudo-Lagrangian vs Eulerian
- SpaceNerdz
- · Replies 1 ·
High School Why didn't the Moon go fully red for this eclipse?
- swampwiz
- · Replies 8 ·
High School Is There a Reference Point for the Expansion of the Universe?
- Sarthak1221
- · Replies 3 ·
High School Comoving distance in cosmology
- Apashanka
- · Replies 1 ·
High School Hyperloop - Orbital Space Launch
- Demigod
- · Replies 28 ·
High School Earth from Space: What Would Hubble See?
- zuz
- · Replies 2 ·
High School Do Black holes reach a critical mass?
- Simon Pratt
- · Replies 3 ·
High School Could Solar Radiation Explain 'Oumuamua's Strange Trajectory?
- .Scott
- · Replies 6 ·
High School The Hubble WFC3 instrument has stopped working
- glappkaeft
- · Replies 2 ·
Undergrad Supermassive black hole eating a stellar black hole
- Joshua Guyette
- · Replies 2 ·
High School Skydiving from Space -- maximum altitude?
- neamt
- · Replies 13 ·
Graduate Hot dark matter constrained by the CMB
- fhenryco
- · Replies 7 ·
High School Missing Dark Matter of NGC1052-DF2
- wolram
- · Replies 1 ·
High School How high can a helium baloon rise to space?
- Deleted member 656102
- · Replies 18 ·
Undergrad Would it be possible to observe an alien city?
- momo666
- · Replies 6 ·
Undergrad Why does an Empty Universe have to obey Negative Curvature?
- Arman777
- · Replies 10 ·
Undergrad How to find the position of a celestial object in the sky?
- Xinran Li
- · Replies 2 ·
Undergrad What is the mass of all photons emitted in the universe?
- Louis Nardozi
- · Replies 13 ·
High School Are White Dwarves Turning into Galactic Disco Balls?
- TEFLing
- · Replies 1 ·
Undergrad What does this description mean? (two bodies orbiting each other)
- n3pix
- · Replies 4 ·
Undergrad Event Horizon and Particle Horizon
- Arman777
- · Replies 12 ·
Stargazing Second repeating fast radio burst discovered by astronomers
- Greg Bernhardt
- · Replies 1 ·
Undergrad Where to find raw data for solar images across wavelengths
- Phylosopher
- · Replies 6 ·
High School Further collapse of Neutron Stars
- Michaela SJ
- · Replies 4 ·
Undergrad Life on Neptune: Could Its Ocean Support Complex Life?
- sjp9220
- · Replies 5 ·
Undergrad Can STEVE's height be calculated from two photos 370km apart?
- astroscout
- · Replies 116 ·
High School Ratio between the sizes of the Observed and the Entire Universe
- Cerenkov
- · Replies 7 ·
Undergrad Moon's eccentricity, apogee and perigee
- darkdave3000
- · Replies 13 ·
Undergrad Confusion about the math of the Comoving Coordinates
- Arman777
- · Replies 8 ·
Undergrad Formation of super-massive black holes
- Green dwarf
- · Replies 2 ·
Undergrad Is inflation needed to explain uniformity?
- Green dwarf
- · Replies 9 ·
High School Probability of our solar system colliding during Andromeda-Milky Way merger
- Glenstr
- · Replies 3 ·
Undergrad Gaia Space Telescope and Lagrangian Point 2
- Johnnyallen
- · Replies 8 ·
Undergrad Sunlight refraction at sunset at different latitudes?
- Mohsin03129
- · Replies 11 ·
Undergrad Why there is no disturbance in orbital paths?
- Kaka
- · Replies 4 ·
Undergrad Metric of the Universe and dependence on Cosmological P
- Arman777
- · Replies 7 ·
Graduate Unification of dark energy and dark matter
- Chris Ian Burkinshaw
- · Replies 1 ·
Undergrad Why Does the Sun Have an Orbital Period Like a Year?
- bunburryist
- · Replies 11 ·
Undergrad Could Our Universe Be a Mirror Image of an Antimatter Universe?
- Anthony Beckwith
- · Replies 6 ·
High School The k term in the Friedmann equation
- Apashanka
- · Replies 2 ·
Undergrad Could old spy satellites be repurposed for astronomy?
- Scott Ryals
- · Replies 6 ·
High School Ideas to protect the Earth from possible asteroid impacts
- Mlesnita Daniel
- · Replies 59 ·
Undergrad Why do we need to unify gravity with the other three forces?
- Green dwarf
- · Replies 3 ·
Undergrad The Expanding Universe and a stationary frame of reference
- darkdave3000
- · Replies 2 ·
Undergrad Footnote on page 151 of Weinberg's Cosmology book
- jouvelot
- · Replies 2 ·
Undergrad Is there any evidence of a universe expansion jerk
- arusse02
- · Replies 3 ·
Undergrad Calculating dark energy and matter density
- Ranku
- · Replies 18 ·
Undergrad Does the universe have zero curvature overall or positive curvature from acceleration?
- harrylentil
- · Replies 9 ·
Undergrad Why will the Milky Way and Andromeda collide if the universe is expanding?
- Sasho Andonov
- · Replies 17 ·
High School Standard candles in a stretching fabric of space
- Rebbyte
- · Replies 3 ·
High School How can galaxies collide if space is expanding?
- Star32503
- · Replies 3 ·
Graduate How Long To 'FreeFall' Into TON 618 From ISCO
- Daharen
- · Replies 3 ·
High School Meaning of the Abbreviation CCH in Graphic
- Sanborn Chase
- · Replies 2 ·
Undergrad Calculating Velocity of a Ball in a Black Hole's Sphere of Influence
- alexchamp29
- · Replies 9 ·
High School Does cosmic expansion affect planets and atoms?
- GraemeSRC
- · Replies 10 ·
High School Why are ds and dω taken as zero for proper distance in FRW cosmology?
- Apashanka
- · Replies 24 ·
Undergrad How does gravity vary in deep mines and interstellar gas?
- KurtLudwig
- · Replies 6 ·
High School Why does the Milky Way have spiral arms with different winding?
- TEFLing
- · Replies 10 ·
Undergrad Do trojan satellites follow migrating planets?
- harrylentil
- · Replies 16 ·
High School Space Time fabric graphic is misleading
- megacal
- · Replies 4 ·
Stargazing What telescope under $1000 can show planetary detail like Mars's polar cap?
- LightMatters
- · Replies 12 ·
High School Water - Where do you think it came from?
- Kay Marie
- · Replies 5 ·
Stargazing Australia's largest optical telescope
- davenn
- · Replies 3 ·
High School Searching for the Ninth Planet: Solar System Migration
- wolram
- · Replies 5 ·
Undergrad Why do transits of Mercury only occur in May and November?
- swampwiz
- · Replies 4 ·